Your monitors moved again? Fix the arrangement

First, check what moved

Two different things can go wrong after sleep or a reconnect. This guide covers the first one: where macOS thinks each screen is.

To check, move the pointer slowly off each edge of each screen. If it leaves where the monitors physically touch, your arrangement is fine.

Why macOS moves your displays

Each monitor tells your Mac who it is: its maker, model and, usually, a serial number. macOS uses that identity to recognize a set of monitors and bring back the arrangement you chose for it. When the identity is missing, duplicated or reported late, macOS can't match the setup and lays the displays out again on its own.

Common causes:

• Two identical monitors that report no serial number, or the same one.
• A dock, hub, KVM switch or adapter that passes the monitor's identity on differently, or presents the displays in a different order after waking.
• Monitors that disconnect completely in deep sleep and come back one at a time.
• Swapped cables or ports, so each monitor arrives on a different connection than before.

Native checks to try first

These cost nothing and fix many setups. None of them can repair a dock or monitor that reports the wrong identity.

1. Set the arrangement again. Open System Settings → Displays, click Arrange, and drag the displays to match your desk. To choose the main display, select it and choose Main display from the Use as menu. Apple describes these options in Displays settings on Mac.
2. Use the same ports and cables every time. Label them if you unplug often.
3. Test without the dock or adapter. Connect the monitors directly for a day. If the problem stops, the dock or adapter is the cause; check its maker for a firmware update.
4. Let every display wake before you rearrange. If you fix the arrangement while one monitor is still waking, macOS may save the wrong one.
5. Check the monitor's own settings. Some monitors have power-saving or automatic input options that make them drop off the connection while asleep.
6. Keep macOS up to date, through System Settings → General → Software Update.

Save the arrangement for each monitor setup

macOS has no way to save a named arrangement and put it back on demand. Universal Display Magnet does this per set of monitors:

1. Open Displays in Universal Display Magnet and drag the screens to where they really are. They snap flush against each other. Snap All closes any gaps.
2. Press Apply. The arrangement goes live and the app asks Keep this arrangement? Choose Keep within 15 seconds, or it reverts by itself.
3. The kept arrangement appears under Saved arrangements for this setup, with Auto-apply on. Turn on Restore resolutions if you also want each display's resolution back.
4. Repeat for each setup you use, such as your desk with the dock and your laptop alone. Each set of monitors keeps its own arrangement.

From then on, when that set of monitors reconnects or macOS moves it, the app applies it again. The setting is Re-apply the saved arrangement when displays connect or macOS moves them, in Settings. The display arrangement page shows the editor in more detail.

What it can and can't tell apart

Universal Display Magnet tells monitors apart by the serial numbers they report. Two identical monitors with different serial numbers are kept separate.

Some monitors and adapters report no serial number, or the same one for both screens. Then the app can't know which physical monitor is which, and two identical screens may swap. Connecting them the same way each time helps. The app also can't fix a dock that drops a display or a cable that fails: if macOS doesn't see a monitor, there is nothing to arrange.

If something looks wrong

• If you don't choose Keep, the previous arrangement comes back after 15 seconds.
• Turn Auto-apply off for one saved arrangement, or turn off the re-apply setting in Settings to stop it everywhere.
• If macOS keeps changing the arrangement back, the app pauses auto-apply for a minute instead of fighting it.
• ⌃⌥⌘D re-applies the saved arrangement when you want it.

Where this has been tested

Universal Display Magnet requires macOS 14 or later and is verified on every version from 14 to 27, on Apple silicon and Intel Macs. It works without a built-in display, including a MacBook with its lid closed. See compatibility for the details.

Monitors fixed, windows still wrong?

Once the screens are in the right place, any windows that moved stay where macOS put them. Restoring windows is a separate step: see Mac windows move after sleep.